And what version of AE? What exactly happens when you try to import? You need to be more precise.
THe version is After Effects CC 2014, could you teach me how to import footage directly from my USB camera?
You may have changed the resolution of the footage in the recording at some point and doesn't recognise it properly.
If you didn't just create a manual Composition and try to import the files there.
Another way is try to auto create a composition with only one file of your footage and try putting the others manually.
And also give us some more info. Is there an error while importing?